New Options

The message list can be configured to show sender name on top, subject on top, and show or hide preview text.

Conversations can be configured to show newest message on top, oldest message on top, and whether to show deleted items in conversations.

The reading pane can be configured to show the reading pane on the right, at the bottom of the screen, or turned off entirely. This can be configured for each folder individually or apply to all folders.

Better visuals.

Buttons are now displayed as blue with white text, rather than pale gray with gray text.

Text word wrapping now works better on smaller displays.

Some icons are larger, such as the A..B..C.. letter separators between contacts in the People tab.

Public Folders

Users will now have rudimentary access to Public Folders from OWA

To add a Public Folder to OWA, users right-click their Favorites menu and click Add Public Folder. They then browse for the Public Folder they want to add. Rinse and repeat for each PF they want to add.

Adding a Public Folder to Favorites also affects the Outlook 2013 client. They will show up there, too.

Only "modern" (Exchange 2013) Public Folders can be accessed. There is no way to view legacy versions of Public Folders.

Only mail Public Folders can be added to Favorites. You cannot view Public Folders that contain calendars, contact items, etc.

At this time users can view, reply, forward, and delete content in Public Folders, but you cannot add new content from OWA.

Help

Help in OWA has been improved by displaying help in a pop-up window, rather than taking over the whole screen. The help window can be moved and positioned, but note that it is not "always on top".

Mobile Devices

In what I consider to be a downgrade, users are no longer able to block mobile devices from syncing with ActiveSync like they could with OWA 2013 RTM.

The icons have also been changed from their more colorful OWA 2013 RTM versions to the stark monochrome versions in OWA 2013 CU1.

Right-Click Functionality

You can now right-click messages to delete them or set a flag. The Move dialog has also been improved to remember your last folders.

You can add an Outlook shared folder to OWA 2013 CU1 by right-clicking your mailbox and select Add Shared Folder. The person who's sharing an Outlook folder must have already configured sharing of the folder in Outlook 2013.

The Small Stuff

If you configure OWA to show week numbers in the Month view, you can now configure when the first week of the year is (first day of the year, first four-day week of the year, or first full week of the year).

More "sort by" options for folders. They now include To and Type.

The search bar now clearly shows that it will search both Mail and People. It always did this, but it didn't clearly indicate that it searches both folders. The search box is also now more visible.

Nothing here is groundbreaking, but it does show that the developer team is continually working on the fit and finish of OWA 2013.